The present invention relates to an improved solenoid. Convention solenoids have an electrically energizable coil consisting of one or more layers of windings about a non-magnetic form producing an electromagnet when the coil is energized, from which form a magnetic armature extends and within which it moves. This armature moves to retracted position when the coil is energized to an extended position under urging from a biasing means when the coil is de-energized. The distance between these positions is known as the "throw" of the solenoid.
Such solenoid devices are widely used for operating circuit breakers, track switches, valves and many other electromechanical devices. They may be used,to operate door locks on cars, in automatic nailer and stapler machines, as electrical motor starters, as contactors on starting equipment, and on fuel racks for diesel engines and the like.
Problems with such conventional solenoids however have limited their applications and usage. For example, with the armature in extended position, because the inner end of the armature is at its position most remote from the corresponding magnetic pole, there is relatively little starting power available to attract the armature into the coil when the coil is energized. As well, the throw is limited by the amount of magnetic strength available when the coil is energized. In practical terms the throw may for instance only be about an inch. In order to overcome these limitations, the number of windings may be increased. Increased windings however result in increased heat being generated when the coil is energized, which heat reduces the ability of the coil to function as an electro magnet and increases wear on the device and components which may surround it.
It is an object of the present invention to provide an improved construction of solenoid which will have increased starting power for the armature, when the coil is energized. It is a further object of the present invention to provide such a solenoid which will permit an increased throw with respect to conventional solenoids. The solenoid according to the present invention provides these advantages without producing the heat build-up which would otherwise be created with additional coil windings. The lower wattage necessary for operation of this solenoid makes it more suitable for feeding with DC power from a battery source than conventional devices.